Protein kinases play a central role in many signaling pathways and are key effectors of cellular functions. As such, protein kinases inhibitors can potentially be developed as therapeutics for many diseases, including cancer, central nervous system disorders and inflammation. Drug discovery efforts have primarily identified small molecule ligands that compete directly with ATP binding. However, molecules that inhibit one kinase by binding at the highly conserved ATP site often inhibit other kinases, resulting in potential drug safety issues. We propose to develop a novel method for in vivo measurement of protein aggregation by monitoring the signals from small fluorophores that have been site-specifically incorporated into the protein during protein synthesis using nonsense suppression methodology. We propose to develop a novel high throughput screening assay to identify non-ATP competitive protein kinase inhibitors with potentially better selectivity and safety profiles. Our assay will identify compounds that allosterically inactivate protein kinases (i.e. stabilize the inactive or "off" state). We will employ a proven model system, Abelson ("Abl") kinase, for the "Proof of Concept" studies. We will develop and optimize the assay to detect inactive and active states of Abl. [unreadable] [unreadable] [unreadable]